For protection of a communication path, it is necessary to set a backup channel for a currently used path. Conventionally, only the path switching by point-to-point has been taken into consideration because of the simplicity of the path setting and the switching condition. In the conventional technique such as SDH and ATM, a static network is basically set by an operator and accordingly, a point-to-point communication using a fixed logical path or a fixed physical path has been mainly used in the communication. However, the connectionless network such as the Ethernet (Ethernet is a trade mark of Fuji Xerox Co., Ltd.) which is mainly used in the network of the current and the next generation is characterized by an automated control such as MAC address learning by STP (Spanning Tree Protocol), the line automatic recognition function of the Ethernet, and a routing protocol in the IP network. These are user-friendly but an operator cannot easily know the path. Furthermore, in a network based on a packet communication, a new concept of multicast and broadcast, i.e., one-to-plurality communication is supported, which also makes the path management difficult together with the introduction of the automatic setting function.
In the NGN (Next Generation Network) configuration, a network system building based on a packet communication is recommended. Moreover, the thigh-speed technique of the Ethernet is being standardized and the application field is increasing from LAN to WAN and a carrier network. Accordingly, the quality of the connectionless communication has become an important object. The multicast function of the connectionless communication such as the Ethernet is and will be an indispensable function when integrating the communication services from now on.
However, the multicast flow communication path changes all the time, depending on the user multicast group participation state or the like. Moreover, even when a multicast path is statistically set, the multicast paths are partially overlapped with one another on the network and it is difficult to know the path to be managed.
On the other hand, the Ethernet is applied to a metro network. The metro region contains a network distributed to a user side, i.e., an individual installation network such as a carrier access network (regional network) and an enterprise site. A ring network provides a mutual connectivity of separate regional networks and connects a user network to a core side (WAN side) providing a wider connection, there by realizing a wide-range communication (enabling use of the Internet).
Assume the form of the broadcast service as a mass medium such as the current television broadcast. It is possible to assume a form that a data stream is distributed to a user from a broadcast station distribution device installed at the WAN side. Here, in the hierarchical network configuration successively containing the regional networks in the WAN side wide-region network, the regional network is connected to the WAN side wide-region network via the ring network. Moreover, as another example, when information is shared by a plurality of region networks or individual sites, the number of cases of using the multicast function is increasing. If the cases require a certain level of quality and confidentiality, it is indispensable to manage the multicast path.
The network using the ring can be classified into the path in which the multicast paths constitute the ring and an individual path which is branched from the ring and proceeds toward a user. In order to avoid the problem of the aforementioned overlap in the individual path, it is possible to assume one of the multicast path protection models as a combination of the ring protection and the linear protection, thereby realizing path management.    Non-Patent Document 1: IEEE P802.1 ag/D5.2, “Virtual Bridged Local Area Networks Amendment 5: Connectivity Fault Management”    Non-Patent Document 2: ITU-T Recommendation G.808.2, “Generic Protection Switching Ring”    Non-Protection Document 3: ITU-T Recommendation T. 1731, “OAM Function and Mechanisms for Ethernet based network”    Non-Patent Document 4: ITU-T Recommendation G. 8031 “Ethernet Protection Switching”    Non-Patent Document 5: IEEE 802.17, “Resilient packet ring (RPR) access method and physical layer specifications”    Non-Patent Document 6: ITU-T Recommendation G. 984.1, “Gigabit-capable Passive Optical Networks (GRON General Characteristics”